1. Field of the Invention
The invention relates to a Faraday cage, particularly for Nuclear Magnetic Resonance applications, having perforated peripheral walls in the form of gratings or networks and grounding means, or means having a predetermined potential with respect to the ground.
2. Description of Related Art
Faraday cages are well known and widely used in combination with Nuclear Magnetic Resonance imaging machines. Faraday cages are reliable means for suppressing electromagnetic noise. This is particularly needed in the so-called dedicated machines, which limit imaging to a few parts or a few areas of the anatomy. In these conditions, the patient body is at least partly outside the magnetic structure of the machine and acts as an antenna for electromagnetic radiation in the environment.
However, these cages typically consist of a room inside a room and are as small as possible, due both to cost and dimensional reasons. By using walls consisting of grates or networks, the problem of lighting up the inner part of the cage by external light sources and of venting the space enclosed in the cage by external or natural means is effectively solved. Nevertheless, the transparency to the eye of the person inside the cage is not sufficient to ensure that he/she will not be seized by clautrophobic crises or other psychological discomfort sensations.
Although various solutions have been proposed for suppressing electromagnetic noise, such as grounding the patient body and/or the medical staff by appropriate arrangements, or using self-shielding equipment, the best solution always includes a Faraday cage electromagnetic shield enclosing the equipment, the patient and possibly the medical staff. Hence, the need arises to provide more attractive Faraday cages.
The invention has an object to provide, by using simple and comparatively inexpensive arrangements, a Faraday cage which provides an effective electromagnetic shield to ensure suppression of noise signals interfering with MRI, while reducing, even in a relatively small volume, the psychological effects on the patient in the cage, particularly improving the visual transparency effect of walls.
The invention achieves the above objects by providing a Faraday cage as described hereinbefore, wherein at least a part of the perforated or grated walls of the cage have a dark color at their inner side, preferably black or the like.
The cage may be composed of prefabricated parts which may be assembled without requiring building works and have a modular construction, allowing installation/dismantling with no masonry works.
The prefabricated parts may be made of an electrically conductive material, preferably metal, and be connected to each other by electrically conductive connection means, also preferably made of metal.
In accordance with a preferred embodiment, both lateral and ceiling walls of the cage, are provided, at least partly and at least for a part of their extension, with a plurality of apertures, whose size and arrangement on the surface depends on the required attenuation of electromagnetic noise.
In this case, at least a few noncritical areas may be provided in the form of continuous walls.
The above arrangements result in a considerable visual transparency, particularly when light sources were only placed outside the cage. Even in relatively poor external lighting conditions, the black color of the inner side of the cage allows, by contrast, a good visibility of the outside environment, thereby reducing the sensation of being enclosed in a confined space.
In equal conditions, the black or dark color allows to reduce the size and/or number of apertures in the wall thereby providing obvious advantages in terms of electromagnetic radiation shielding.
Advantageously, according to an improvement, the entrance doors may have, on its inner side, a color which differs markedly from the rest of the cage, particularly a light or white color, such as to allow an occupant to locate immediately the exit.
The provision of these apertures allows the patient to stay comfortably inside the cage, and to get over the discomfort caused by the necessarily long permanence inside confined rooms and/or situations, without limiting the function of the cage as an electromagnetic shield.
In accordance with an advantageous improvement, the cage may have, in combination with the doors, ceiling construction parts which can be opened and closed at the same time as doors.
Here advantageously, the doors are of the sliding type and extend to the ceiling, and are connected to the adjacent ceiling parts, at least one sliding guide, preferably two sliding guides, especially three sliding guides being provided, at the lower end of the door panel, at the upper end of the area connecting to the ceiling part and at the free end of the ceiling part opposite to the door panel.
The frame or the peripheral ledges of the door wings and/or the corresponding contact and/or abutment edges of the side frames may be provided with electric contact generating means along their extensions.
These electric contact generating means consist, at least partially and/or at least on the panel and/or at least on the side frame, of electric contact generating means which may be elastically stressed against the contact surface and/or wiping contact generating means.
These arrangements allow that the panel have a good electric continuity between themselves and between each of them and its respective side frame part, such that, in the closed condition, sufficient electric conductivity characteristics may be maintained. More particularly, the cage parts provided with entrances have the same shielding characteristics as all the other parts of the cage.